PHARMACOLOGICAL ACTIONS OF A CONVULSANT BARBITURATE [SODIUM 5-ETHYL-5-(l,3-DIMETHYLBUTYL) BARBITURATE] I. STIMULANT AND DEPRESSANT EFFECTS

¹ Department of Pharmacology, University of Michigan, Ann Arbor

The central nervous system effects of a convulsant barbiturate, sodium 5-ethyl-5-(1,3-dimethylbutyl) barbiturate, were compared with the actions of pentobarbital in cats. Depending upon the dose, the convulsant barbiturate has both stimulant and depressant properties.

Under special conditions the convulsant barbiturate was shown to increase the mean convulsant dose of a timed intravenous infusion of pentylenetetrazole. Comparable amounts of pentobarbital were much more effective in increasing the mean convulsant dose of pentylenetetrazole. The depressant actions of the convulsant barbiturate appear to be real and not secondary to the stimulant effects.

The low to medium-voltage, medium to fast-frequency pattern observed in the EEG with the convulsant barbiturate was still present in three of five mesencephalic preparations verified by autopsy to be complete transections. In the remaining two preparations the convulsant barbiturate reduced the frequency of spindle bursts and prolonged the interval between bursts in a manner similar to that of pentobarbital.

The convulsant barbiturate enhanced the crossed-extensor reflex elicited by electrical stimulation of the contralateral sciatic nerve while pentobarbital depressed this response. However, prior abolition of the crossed-extensor reflex by pentobarbital was not antagonized by small doses of the convulsant barbiturate. Simple observations of an intact animal given the convulsant barbiturate offer no clue to primary depressant effects. Such depressant properties are observed only with a more precise neuropharmacological analysis.